Yeah its quite common, when it first happened to mine about 5 months ago quite a few people responded saying it had happened to them. It was replaced under warrenty by Renault Birmingham, the only problem was thay had for a day to find the problem ( even though I had told them what it was ) then had to have it back another day because they had to order the part in !! Had no problems since !!
I was told by renaul that it was a crack in the moulding on the bottle. was going to look at it myself but couldnt be ars*d to take the wipers off !!